Stuff is changed now that Desmond has been back to his past a few times but when he returns, it is only in his mind that anything has changed. I'm not sure how this affects his actions but I'm not sure it sticks with him over time. Meaning, I don't think that he probably held the phone number in his head for 8 years.

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"I saw a guy lying there with an ankle holster. So I took the gun. Thought it might come in handy. And guess what? I just shot a bear!"